How would I mock the DataSource from TypeORM in NestJS Jest tests? - node.js

Question

I am trying to write tests for a small project in NestJS. Here is the relevant code for context:
dummy.controller.ts
#Controller(UrlConstants.BASE_URL + 'dummy')
export class DummyContoller {
constructor(
private readonly sessionService: SessionService,
) { }
#Get('validateSession')
async checkValidateSession(#Query('sessionId') sessionId: string) {
const session = await this.sessionService.validateSession(sessionId);
console.log(session);
return { message: "OK" };
}
}
session.service.ts
#Injectable()
export class SessionService {
constructor(
private readonly sessionRepo: SessionRepository,
private readonly accountRepo: AccountRepository
) { }
#WithErrorBoundary(AuthCodes.UNKNOWN_LOGIN_ERROR)
async validateSession(sessionId: string) {
const session = await this.sessionRepo.findOneBy({ sessionId });
if (!session || this.isSessionExpired(session)) {
session && await this.sessionRepo.remove(session);
throw new HttpException({
code: AuthCodes.SESSION_TIMEOUT,
message: AuthMessages.SESSION_TIMEOUT
}, HttpStatus.UNAUTHORIZED)
}
return session;
}
...
}
session.repository.ts (Any repository)
#Injectable()
export class SessionRepository extends Repository<Session> {
constructor(private dataSource: DataSource) {
super(Session, dataSource.createEntityManager())
}
...
}
This is how I wrote my test (this is my first time writing a test using Jest and I am not really experienced in writing tests in general):
describe('DummyController', () => {
let dummyContoller: DummyContoller;
let sessionService: SessionService;
let sessionRepo: SessionRepository;
let accountRepo: AccountRepository;
beforeEach(async () => {
const module = await Test.createTestingModule({
controllers: [DummyContoller],
providers: [SessionService, SessionRepository, AccountRepository]
}).compile();
dummyContoller = module.get<DummyContoller>(DummyContoller);
sessionService = module.get<SessionService>(SessionService);
sessionRepo = module.get<SessionRepository>(SessionRepository);
accountRepo = module.get<AccountRepository>(AccountRepository);
})
describe('checkValidateSession', () => {
it('should return valid session', async () => {
const sessionId = "sessionId1";
const session = new Session();
jest.spyOn(sessionService, 'validateSession').mockImplementation(async (sessionId) => session);
expect(await dummyContoller.checkValidateSession(sessionId)).toBe(session);
})
})
})
Upon running the test, I encounter:
Nest can't resolve dependencies of the SessionRepository (?). Please make sure that the argument DataSource at index [0] is available in the RootTestModule context.
Potential solutions:
- If DataSource is a provider, is it part of the current RootTestModule?
- If DataSource is exported from a separate #Module, is that module imported within RootTestModule?
#Module({
imports: [ /* the Module containing DataSource */ ]
})
I looked this problem and I came across a number of solutions but most of them had #InjectRepository() instead of creating a separate Repository class where they would provide getRepositoryToken() and then use a mock factory [Link]. I couldn't find a way to make this work.
Another solution suggested using an in-memory database solution [Link]. But this felt more like a hack rather than a solution.
How can I test the above setup?

Answer 1

Based on this comment, I was able to get this working by using the following in the providers in the test:
providers: [
SessionService,
{ provide: SessionRepository, useClass: SessionMockRepository },
]
SessionMockRepository contains a mocked version of all additional functions in that particular repository:
export class SessionMockRepository extends Repository<Session> {
someFunction = async () => jest.fn();
}
Currently, this works for me so I am accepting this. I am still open to more answers if there is a better way to do this.